The final chapter of the Harry Potter series may have been closed, but it looks like fans of the boy wizard can look forward to new adventures as author JK Rowling turns her hand to an online game.

It is thought Rowling's new project, due to be officially launched on Thursday, will be a Potter-based treasure hunt entitled Pottermore, after an apparently secret memo emerged.

The new project is reportedly an online game that gives users clues which will lead them to prizes hidden in the real world. Aspiring wizards the world over can hope to find an undisclosed number of magic wands stashed throughout the UK and US, and possibly other countries. It is not yet clear if the treasure hunt is Pottermore itself or a marketing drive for another product, and details about the game remain hazy.

News of the project emerged after the Times appeared to have been sent a memo by mistake, although it is not known if it was sent as a marketing device. PR company Adam & Eve appears to be behind the project, and has, in the past, conducted online treasure hunts using Google maps. Last year it created LittleBigMap, a game designed to promote the video game LittleBigPlanet 2, which encouraged users to find new markers on the map by following clues.

Rowling, who is due to make an announcement at the Victoria and Albert Museum in south-west London, has stated that the seventh Harry Potter book is the last in the series. "I've got enough story for seven books and I never planned to carry the story beyond the end of book seven," she wrote on her website. "I might do an eighth book for charity, a kind of encyclopaedia of the world so that I could use all the extra material that's not in the books ... we'll see!"

The author has already produced two spin-off books published for charity, Fantastic Beasts and Where to Find Them, and Quidditch Through the Ages.

Rowling is known to make Potter announcements through the fan websites dedicated to everything Potter, and is thought to have given sneak previews of Thursday's announcement to some. Andrew Sims, of Mugglenet, did little to curb excitement around the announcement, saying only that the new project was "fantastic". He wrote: "[I] can tell you that it is fantastic. I'd say more but I had to make an unbreakable vow concerning its secrecy."